# 1+2+3+...+100=?
sum = 0
for i in range(100):
    sum = sum + (i+1)
print(f"1+2+3+...+100 = {sum}")

# 2
sum = 0
for i in range(1, 101):
    sum=sum+i
print(f"1+2+3+...+100 = {sum}")

# 3
sum = 0
for i in range(1, 101):
    sum += i
print(f"1+2+3+...+100 = {sum}")

#4
a     = 1
b     = 100
count = b-a+1
sum = (a+b)*count//2
print(f"1+2+3+...+100 = {sum}")